In reviewing the proposed "Internet Application Protocol Collation
Registry" (http://www.ietf.org/internet-drafts/draft-newman-i18n-comparator-12.txt),
it became clear that the possible options in UCA are called out in the
algorithm and document, but not clearly organized and named. In particular,
they are given attribute names and values in CLDR; those should be also used
in UCA. For the CLDR attribute names & values, and what they mean, see the
Table "Collection Settings" in
http://unicode.org/reports/tr35/#Collation_Elements. Here is a list of
the options, with a fragment of text in UCA where they occur, and the
corresponding CLDR options.

E. Strength (Level)

UCA Text: An implementation may allow the maximum level to be set
to a smaller level than the available levels in the collation element array.

CLDR Attibute: strength (UCA default ="3")

F. Semi-Stable

UCA Text: S3.10 If a semi-stable sort is
required, then after all the level weights have been added, append a copy of
the NFD version of the original string.

CLDR Attribute/value: strength="identical"

Note: CLDR doesn't allow the semi-stable option except with all
weight levels, so having it as a "higher" weight level works. That
should also be followed in UCA.

G. Preprocessing

UCA Text: 5.1 Preprocessing....Such preprocessing is outside of the scope
of this document.

CLDR Attribute: numeric (UCA default="off")

CLDR Attribute: caseLevel (UCA default="off")

CLDR Attribute: caseFirst (UCA default="off")

CLDR Attribute: hiraganaQuaternary (UCA default="off")

CLDR Attribute: variableTop (UCA default="off")

In UCA we probably just want to point to CLDR as examples of options, but
not make these options for UCA

H. Matching

UCA Text: Section 8

Note a typo, where sometimes the term "Whole Grapheme Clusters Only"
is used, and sometimes "Whole Characters Only"; this needs fixing. Also,
the discussion should call out the common matching operations "startsWith"
and "endsWith": in particular, it should clarify that these tests return
true if and only if there is a maximal match at the start (and end,
respectively): the choice of medial or minimal matches would only affect
additional (optional) returned positioning information.